It is said that PAPS of a structure represented by the formula: ##STR1## serves as the sulfate donor for all sulfation reactions known to occur in the cells of higher animals. In higher animals, sulfation reactions are involved in a variety of biochemical/physiological processes which include the detoxication of xenobiotics, the metabolism of catecholamine-type of neurotransmitters, the biosynthesis of sulfated proteins and sulfated proteoglycans. There have also been reports showing a correlation between the sulfation level of biomolecules and the cellular oncogenic transformation. Namely, PAPS plays very important roles in vivo and, therefore, it is highly useful in the fields of, for example, drugs. However, none of the known methods for producing this compound is applicable on an industrial scale or has been put into practical use. As an example of a method for chemically synthesizing PAPS, the one reported by Robert et al. may be cited [refer to R. Cherniak et al., J.B.C., 239, 2986 (1964)]. As an example of a fermentation method for producing PAPS, a method with the use of a bacterium belonging to the genus Streptomyces is reported [refer to JP-B-41-17632; the term "JP-B" as used herein means an "examined Japanese patent publication"]. Examples of known methods for enzymatically producing PAPS include those wherein PAPS is produced from adenosine 5'-triphosphate (hereinafter referred to simply as ATP) by a two-stage reaction with the use of adenosine 5'-triphosphate sulfurylase (hereinafter referred to simply as ATP sulfurylase) and adenosine 5'-phosphosulfate kinase (hereinafter referred to simply as APS kinase) extracted from baker's yeast [refer to "Methods in Enzymology", ed. by S. P. Colowick, N. O. Kaplan, P. W. Robbins., 5, 964, Academic Press Inc., New York and London, 1962, ] or rat liver [refer to S. S. Singer, Anal. Biochem., 96, 34 (1979)].
However, each of these methods makes it possible to produce only several to several tens of milligrams of PAPS and, therefore, is of no practical use from an industrial viewpoint. That is to say, the chemical methods cannot be scaled up since reagents which are difficult to handle and a complicated reaction are needed therein. In the fermentation methods, only a trace amount of PAPS is accumulated and it is very difficult to separate this product from cells or media. By the enzymatic synthesis of PAPS, one molecule of PAPS is formed from two molecules of ATP and one molecule of adenosine 5'-diphosphate (hereinafter referred to simply as ADP) is simultaneously formed as a side product, as the following (chemical equation 4) shows. Therefore, the enzymatic methods are disadvantageous in that the yield of PAPS, based on the ATP, is 50% at the highest. ##STR2## In the above chemical equations, PPi is pyrophosphoric acid and Pi is phosphoric acid. As described above, it is very difficult to produce PAPS on an industrial scale.
It is an object of the present invention to provide a method for producing PAPS from ATP by a two-stage reaction with the use of at least two enzymes, i.e., ATP sulfurylase and APS kinase, whereby PAPS can be produced in a large amount and easily isolated.